This invention relates to hydrostatic testing devices and, more particularly, to an improved hydrostatic test apparatus for pressure testing fire hoses and the like, and pressure vessels such as fire extinguishers. The invention provides a compact, portable and inexpensive test apparatus which may be operated by a single individual and is very safe in use as it operates on very low volumes of water. Use of this invention for testing fire hoses and the like eliminates the necessity of using a standard pumper truck for hose testing purposes, an operation which is both expensive and dangerous.
Ordinarily, regulations in most areas require fire stations to pressure test new hoses before they are put into service and to test all hoses periodically, at least once a year, and in many cases, twice a year. On average, each fire company has 50 to 65 sections of hose which are from 11/2 inches to 5 inches in diameter. These hoses are stored in the bed of each pumper truck and are coupled together, ready for use, or stored in storage racks. When testing is required, the station pumper truck is used to pressure test the fire hose. This is an expensive operation because the better part of a day is required if all hoses are checked at one time and the assistance of all station personnel is necessary to accomplish the task. This means that the station is out of service and adjacent stations must be assigned to cover the out of service station's territory. Due to the relatively high pressures required for testing hose, the pumper truck used may be damaged and repairs may prove to be very expensive; ordinarily, a new pumper truck costs as much as $200,000.
Other problems encountered in using a pumper truck to test hose are manifold. New hose is tested at about 300 PSI in order to ensure that the hose meets specifications. Old hose and new hoses which are 4 or 5 inches in diameter are pressure tested at 250 PSI. A pumper truck has a centrifugal pump which is adapted for moving large volumes and not for hydrostatic loading. A static, overload condition creates excessive heat resulting in unneccessary pump wear and stress to the pumper truck's drive system. There is also the cost of fuel to be considered because the pump runs off the engine. Standard pumper truck pumps are single or two stage pumps which require very high speeds to reach the test pressures of 250-300 PSI. For example, a pumper is designed to deliver 50% of its capacity at 250 PSI. When test pressures of 300 PSI are required, against deadhead conditions, the pump is drastically overworked.
Attempts have been made in the past to provide testing devices for pressure testing fire hoses which do not require the use of the station's pumper truck. U.S. Pat. No. 3,362,225 issued to M. A. Noble is directed to such a pressure testing device. The unit has a dual piston water pressure operated pump and sequencing valves. Water under pressure may be supplied from a hose connected to an ordinary water tap. The pistons continue to raise pressure in the hose to be tested until the desired pressure of 200 PSI to 600 PSI is reached, as indicated on a pressure gauge. The pump is stopped by shutting off the water supply from the tap. Pressure is maintained as long as desired to complete the testing procedure. Thereafter, water is drained from the apparatus and the hose being tested is disconnected. This device is complex and requires special, customized components made for the unit. Additionally, no means are disclosed for purging air from the test device. Air in the test device or hose being tested presents an obvious danger, in case of hose rupture during the test, and the test results will be inaccurate because air entrained into the system will be compressed, thus resulting in erroneous test pressure readings.
U.S. Pat. No. 4,103,537 issued to F. R. Victor discloses a portable pressure testing apparatus for water mains or the like including a motor, a pump driven by the motor, flow control valving, a relief valve and a pressure gauge. A bleeder valve and container are provided for measuring leakage in the main being tested. However, the apparatus disclosed includes no air venting arrangement of the type employed in this invention. Additionally, no bypass line with a pressure relief valve is disclosed which would provide for constant pressures once the system is filled.
Another known device includes a manifold arrangement for testing multiple lengths of hoses simultaneously. A water inlet valve is provided and a bleeder valve is included to bleed air from the system. A source of air under pressure must be provided together with an air pressure gauge in order to test the hoses. The principal difficulties with this system are that erroneous pressure readings result because air is used to pressurize the system and the air becomes entrained in the water filling the system and is compressed. Additionally, an expensive compressor or source of high pressure air is required to operate this testing device.